The city has begun grilling 3,200 World Trade Center rescue and recovery workers who have filed claims seeking compensation for respiratory and toxic injuries, The Post has learned.

Up to 60 workers a day have been scheduled in back-to-back hearings to answer the city’s questions under oath.

The city can require the “50-h” hearings before claimants can go to court. Each hearing takes about three hours, city officials told The Post.

Lawyers hired by the city to conduct the questioning are being paid up to $330 or $480 an hour, according to an outside firm, Patton Boggs. At that rate, the city’s legal cost will total at least $3.1 million.

Law Department spokeswoman Connie Pankratz said the firm has a “special rate arrangement” and that the actual fees are less.

“By law, the city has a right to conduct these hearings,” the department said. “Given the plaintiffs’ copious litigation – and the need to gather accurate information and assess each claim fairly – the city would be utterly remiss not to investigate each claim thoroughly.”